Refer to the exhibit. Router B and router C are performing mutual redistribution between
OSPF and EIGRP, and their default metrics are configured the same. Router D has equal
cost paths to networks where both paths are not really equal cost. For example, network
172.16.54.0 shows equal cost through both router B and router C, though in reality the cost
is greater using router C. Other routers, though not shown, are connected to the 172.16.54.0
and 172.16.55.0 networks, and the same issues exist to those routers and the networks
connected to them. What can be done so that data will be routed along the most optimal
path in the network?
Select the best response.
A.
Redistribute connected interfaces on router B and router C.
B.
Set the maximum number of equal cost paths to 1 in all routers.
C.
When redistributing EIGRP into OSPF, set the external metric type to type E1.
D.
Adjust the default metrics in router B and router C so that the values are different in each
router.
E.
None of these solutions will fix the problem. Migrate to a single dynamic routing protocol.
Correct answer is C.
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Let’s discuss about answers C & D first.
From the output, we learn that all the External OSPF routes have metrics of 100 (the second parameters in [110/100]). This is not the default metric of OSPF Type 2 External route (the default value is 20) so the metrics of redistributed routes have been modified. Maybe when redistributing into OSPF, the “metric” in the “redistribute” command or the “default-metric” command was used on router B & C to assign the metric of these routes. Something like this:
router ospf 1
redistribute eigrp 1 metric 100 subnets
or
router ospf 1
…..
default-metric 100
Therefore even if we use the metric type E1 the problem still exists because the link B-D & C-D seems to have the same metric -> the total metrics remains the same -> C is not correct.
We can use route-map and set different metrics for each networks but some unshown networks will have the same issues -> D is not a good choice
So the best answer should be E.
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